The invention relates generally to energy discrimination radiography for inspection of industrial components and, more particularly, to energy discrimination digital radiography for material characterization of industrial components.
Nondestructive evaluation (or testing) continues to gain prominence for the inspection of industrial components, such as turbine blades, castings, welded assemblies, and aircraft fuselage frames. The objectives of nondestructive testing include detecting, quantifying and locating inclusions and corrosion in metallic components and assessing the relative and absolute amounts of two or more materials in components of simple or generally complex geometry. Examples of such applications include determination of the amount and location of water in aluminum honeycomb, determination of the amount and location of corrosion in metallic aircraft structures, and determination of the amount and location of residual ceramic core in cast aeroengine turbine blades.
Radiographic imaging is a useful tool for the nondestructive evaluation of industrial components, such as turbine blades. However, despite recent advances in digital radiography technology, the radiographic detection of one material, particularly small amounts of that material, residing in a complex structure of another material remains problematic. Moreover, corrosion can be difficult to detect and quantify using conventional radiographic techniques. This is especially true for minor corrosion. Significant corrosion often results in reduced material in the region of interest, which in turn reduces the X-ray absorption during inspection, such that the significant corrosion can be detected using conventional radiographic inspection techniques. However, minor corrosion products can remain on the structure, and the added oxidized component of the corrosion can actually increase the absorption of X-rays during inspection. In the resulting image, the minor corrosion can appear much like an adhesive used to bond parts of the structure, thereby masking the presence of the corrosion and inhibiting its detection using conventional radiographic techniques. Other issues arise where the added X-ray absorption of the corrosion oxidizers offsets the reduction in the metal structure from lost corrosion products, making detection and quantification of the corrosion difficult using conventional radiographic techniques.
These limitations of conventional radiographic techniques stem from the fact that conventional radiographic imaging of industrial components consists of single spectrum imaging, which is limited by complex overlapped features, as well as feature shape-dependent and contrast-dependent algorithms. Consequently, material characterization of industrial components, including the detection and quantification of minor corrosion, is complicated by conventional radiographic techniques.
Accordingly, it would be desirable to provide a radiographic imaging technique with enhanced material characterization capabilities. In addition it would be desirable to provide a radiographic imaging technique for imaging complex, multi-constituent industrial components. It would further be desirable for the radiographic techniques to increase the speed of detectability, as well as the quantifiability of the amounts of different materials in an industrial component.